There has been a concerted effort in manufacturing industries to increase the precision with which manufactured parts are fabricated. In addition to precision, a long sought after goal has been the development of an apparatus which is able to automatically fabricate parts with as little human intervention as possible and to do so with efficient utilization of the manufacturing apparatus.
Many different apparatus have been proposed and actually implemented in an effort to achieve that goal. All have suffered from insufficient automation and inefficient utilization. More specifically, many of the functions of the machining apparatus still had to be performed by a human operator and, for too much of the time, the machining apparatus was idle and not performing an actual machining operation. For example, should there have been a failure in some part of what purported to be the automated control circuitry for the machining apparatus, the apparatus would no longer be able to proceed with a machining operation until the failure was rectified. In other instances, delivery of parts, tools, and operating instructions were not efficiently managed so that the machining apparatus was not machining for as much of the time as possible.
One of the earliest attempts to automate a machining operation was a numerically controlled machining apparatus which moved a cutting element with respect to a workpiece along a cutting path stored on a recording medium such as magnetic tape or punched paper tape. All this arrangement accomplished was to free the machine operator from manually moving the cutting element to machine the workpiece. It did not eliminate the need for a human operator or provide for a significant increase in machine utilization.
Improvements to numerically controlled machining apparatus involved computerizing the numerical controller. This provided some measure of computational ability for the controller, which permitted it to do such things as calculate offsets to a part program.
A further effort, called distributed numerically controlled machining, involved connecting a number of computerized numerically controlled machining apparatuses to a host computer which was intended to coordinate the activities of all the machining apparatus.
In an attempt to completely automate a production facility, it has been proposed that automated part and tool storage apparatus, along with automated guided vehicles for carrying tools to be used for machining and parts to be machined to and from the storage apparatus and the machining apparatus, be coordinated through a host computer in a distributed numerically controlled machining system. In one form of such a distributed numerically controlled machining system, also known as a flexible machining system, each of the parts to be machined is attached to an appropriate fixture in a staging area associated with the part storage apparatus. The fixture permits each part to be attached to one of a plurality of different machining apparatus, such as a lathe, a grinder, a vertical machining center, and the like. An automated guided vehicle then transports the part attached to a fixture to an appropriate machining apparatus in accordance with instructions from the host computer. Also in a flexible machining system, a plurality of tools are loaded into a magazine at the tool storage apparatus and the magazine is transported to an appropriate machining apparatus in accordance with the instructions from the host computer. The host computer electronically transmits or down loads one or more machining instructions comprising machining programs to appropriate machining apparatus, which then machines the part delivered to it using the tools in the magazine, all in accordance with the machining programs.
The prior practices and proposals either fail to address or inadequately deal with items which permit unattended and efficient operation of machining apparatus. This has prevented the implementation of a completely automated multiple purpose production facility. Briefly, not enough of the functions of the machining apparatus have been automated to reduce significantly the number of human operators needed to run the machining apparatus. Also, too much of the automation that does exist resides in the host computer in the prior distributed numerically controlled machining systems and in the flexible machining systems. This means that, if the host computer were to cease functioning for some reason, the entire factory would cease to function. Without the host, the individual machining apparatus used in the past are just incapable of carrying on in any meaningful fashion.
The invention of this application addresses the problems of the prior machining systems and permits for the first time the actual implementation of a completely automated factory with a minimum of human attention.